PREAMBLE
The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and professional organization founded in 1954 to promote the science, technology and practical application of nuclear medicine. Its 16,000 members are physicians, technologists, and scientists specializing in the research and practice of nuclear medicine. In addition to publishing journals, newsletters, and books, the SNMMI also sponsors international meetings and workshops designed to increase the competencies of nuclear medicine practitioners and to promote new advances in the science of nuclear medicine. The European Association of Nuclear Medicine (EANM) is a professional nonprofit medical association that facilitates communication worldwide between individuals pursuing clinical and research excellence in nuclear medicine. The EANM was founded in 1985.
The SNMMI/EANM will periodically define new guidelines for nuclear medicine practice to help advance the science of nuclear medicine and to improve the quality of service to patients. Existing practice guidelines will be reviewed for revision or renewal as appropriate, on their fifth anniversary or sooner, if indicated.
Each practice guideline, representing a policy statement by the SNMMI/EANM, has undergone a thorough consensus process in which it has been subjected to extensive review. The SNMMI/EANM recognizes that the safe and effective use of diagnostic nuclear medicine imaging requires specific training, skills, and techniques, as described in each document.
The EANM and SNMMI have written and approved these guidelines to promote the use of nuclear medicine procedures with high quality. These guidelines are intended to assist practitioners in providing appropriate nuclear medicine care for patients. They are not inflexible rules or requirements of practice and are not intended, nor should they be used, to establish a legal standard of care. For these reasons and those set forth below, the SNMMI/EANM cautions against the use of these guidelines in litigation in which the clinical decisions of a practitioner are called into question.
The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by medical professionals taking into account the unique circumstances of each case. Thus, there is no implication that an approach differing from the guidelines, standing alone, is below the standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set forth in the guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources, or advances in knowledge or technology subsequent to publication of the guidelines.
The practice of medicine involves not only the science but also the art of dealing with the prevention, diagnosis, alleviation, and treatment of disease. The variety and complexity of human conditions make it impossible to always reach the most appropriate diagnosis or to predict with certainty a particular response to treatment. Therefore, it should be recognized that adherence to these guidelines will not ensure an accurate diagnosis or a successful outcome. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources, and the needs of the patient to deliver effective and safe medical care. The sole purpose of these guidelines is to assist practitioners in achieving this objective.
I. INTRODUCTION
18F-fluorodeoxyglucose (18F-2-fluoro-2-deoxyglucose or FDG) positron emission tomography (PET) and PET/CT are noninvasive diagnostic imaging procedures providing tomographic images for the determination of localized metabolic activity. Fluorine-18 (18F) is a cyclotron-produced radioisotope with a half-life of 109.7 min that undergoes positron decay. 18F-FDG is an analog of glucose and is taken up by living cells via cell membrane glucose transporters and subsequently phosphorylated with hexokinase inside most cells. 18F-FDG has been proposed for imaging infection/inflammation in part because it has been seen at sites of infection/inflammation during routine 18F-FDG imaging of cancer patients. Further studies showed that cells involved in infection and inflammation, especially neutrophils and the monocyte/macrophage family, are able to express high levels of glucose transporters, especially GLUT1 and GLUT3, and hexokinase activity (1–5). From limited experimental studies, it seems that the ability of the procedure to identify sites of inflammation and infection is related to the glycolytic activity of the cells involved in the inflammatory response. Many types of cells are involved in this process although no single cell was found specifically and consistently involved in all models. In addition, enhanced glucose consumption and subsequent 18F-FDG uptake can also be the result of a stress reaction of the affected cells in response to cell damage (metabolic flare) (6).
II. GOALS
The aim of this guideline is to provide general information about performing 18F-FDG PET or PET/CT in inflammation and infection. We provide evidence for efficacy where it is available, but the use of 18F-FDG imaging in inflammation and infection is rapidly evolving and these guidelines cannot be seen as definitive. Therefore, the indications mentioned within this guideline should be regarded as current advice and areas for clinical research rather than as fully approved clinical indications. Despite the limited literature available on the use of 18F-FDG imaging in these indications, it is clear that the use of metabolic imaging using 18F-FDG, together with morphologic imaging, that is, PET/CT or fusion of PET and CT data (further referred to as 18F-FDG imaging), is becoming the scintigraphic method of choice. It can be expected that after further validation, PET/CT may become a first-line tool in these nononcologic indications.
This guideline complements the EANM and SNMMI guidelines for the use of 18F-FDG PET for tumor imaging (7,8) and, to avoid duplication, will not reproduce any statements that overlap. These include information concerning PET or PET/CT camera performance and quality control, general acquisition parameters, radiopharmaceutical acceptance, and general basic and clinical aspects of 18F-FDG imaging that may apply to both tumor and infection/inflammation imaging. The present guideline aims to provide the user with basic knowledge of and competence in the use of 18F-FDG imaging in the field of inflammatory and infectious disorders.
III. DEFINITIONS
This section is not applicable.
IV. COMMON CLINICAL INDICATIONS
No appropriateness criteria have been developed to date for this procedure. The development of 18F-FDG in this field is rapidly evolving, especially since the emergence of PET/CT. Table 1 summarizes the indications that have been reported in the literature with various success rates. The list is based on an evaluation of scientific peer-reviewed publications (at least with an abstract in English allowing the evaluation of the study) from 1994 to December 2011. Only original publications with more than 10 patients and with the possibility of calculating the diagnostic sensitivity, specificity, and accuracy were taken into consideration.
Published Studies with More Than 10 Patients Before December 2011
Although there is still insufficient literature for this to be described as an evidence-based indication, we can conclude, on the basis of a cumulated reported accuracy (>85%) and expert opinion that major indications for 18F-FDG PET/CT in infection and inflammation are as follows:
Peripheral bone osteomyelitis (nonpostoperative, non–diabetic foot) (16–23).
Suspected spinal infection (spondylodiskitis or vertebral osteomyelitis, nonpostoperative) (24–28).
Evaluation of fever of unknown origin (FUO) (29–44), including true FUO (defined according to the criteria of Durack and Street (44)), postoperative fever and recurrent sepsis, immunodeficiency (both induced and acquired)-related FUO, neutropenic fever, and isolated acute-phase inflammation markers (persistently raised C-reactive protein and/or erythrocyte sedimentation rate).
Evaluation of metastatic infection and of high-risk patients with bacteremia (32).
Primary evaluation of vasculitides (e.g., giant cell arteritis) (45–56).
Other well-described applications, but without sufficient evidence-based indication, include the following:
Evaluation of potentially infected liver and kidney cysts in polycystic disease (56–63).
Suspected infection of intravascular devices, pacemakers, and catheters (64–71).
AIDS-associated opportunistic infections, associated tumors, and Castleman disease (72–83).
Assessment of metabolic activity in tuberculosis lesions (84–87).
Considering the available published data, it is unclear if 18F-FDG imaging offers any significant advantage over radiolabeled white blood cells or antigranulocyte monoclonal antibodies in the following situations:
It must be emphasized that large prospective studies comparing different nuclear medicine procedures are often lacking. Nevertheless, the level of evidence available at this time for many of these indications remains insufficient to strongly advise the use of 18F-FDG imaging as a first-line diagnostic tool. The level of evidence is at best at Cochrane grade B, especially for true FUO, spinal infection, and vasculitis. The level of evidence is lower (Cochrane C or D) for other indications. It must be kept in mind that the choice between 18F-FDG imaging and an alternative technique may depend on the need for rapid diagnosis and local availability of equipment and labeled agents. For example, some specific indications such as the evaluation of vascular prostheses and the diabetic foot absolutely require the use of hybrid PET/CT for precise anatomic localization of the 18F-FDG uptake.
V. REGULATORY ISSUES
There is consistent progress in the field, with regular new literature and registration of 18F-FDG for several indications by the European Medicines Agency. In the United States 18F-FDG is not approved by the Food and Drug Administration for indications other than oncology, cardiology, and epilepsy (120).
VI. QUALIFICATIONS AND RESPONSIBILITIES OF PERSONNEL
In the United States, see the SNMMI Guideline for General Imaging and the SNMMI Guideline for Tumor Imaging with 18F-FDG PET/CT (8). In Europe, the certified nuclear medicine physician who performed the study and signed the report is responsible for the procedure, according to national laws and rules.
VII. PROCEDURE/SPECIFICATIONS OF THE EXAMINATION
A. Request
The request for the examination should include sufficient medical information to demonstrate medical necessity and should include the diagnosis, pertinent history, and questions to be answered. The medical record should be reviewed. Relevant laboratory tests should be considered. When available, the results of prior imaging studies should be reviewed, including plain-film radiography, CT, MRI, bone scanning, and 18F-FDG PET/CT. Relevant prior studies should be directly compared with current imaging findings when possible.
B. Patient preparation and precautions
The major goals of preparation are to minimize tracer uptake in normal tissues, such as the myocardium, skeletal muscle, and urinary tract, while maintaining uptake in target tissues.
Pregnancy (suspected or confirmed)
In the case of a diagnostic procedure in a patient who is known or suspected to be pregnant, a clinical decision is necessary to consider the benefits against the possible harm of performing any procedure. The International Committee for Radiation Protection (ICRP) reports that the administration of 259 MBq (7 mCi) of 18F-FDG results in an absorbed radiation dose of 4.7 mGy to the nongravid uterus (i.e., 1.8 × 10−2 mGy/MBq) (121). Direct measurements of 18F-FDG uptake in a case study suggested higher doses to the fetus than currently provided in standard models (122). A pregnancy test may help with the decision, provided the 10-d postovulation blackout is understood. In case of doubt and in the absence of any emergency, the 10-d rule should be adopted.
Breastfeeding
The ICRP does not recommend interruption of breast feeding after 18F-FDG administration since little 18F-FDG is excreted in the milk (121). However, the suggestion may be made that contact between mother and child be limited for 12 h after injection of 18F-FDG to reduce the radiation dose that the infant receives from external exposure from the mother. It is recommended that the infant be breastfed just before injection, to maximize the time between the injection and the next feeding.
Diabetes and serum glucose level before 18F-FDG administration
It has been advocated that high serum glucose levels may interfere with the targeting of inflammatory and infectious sites because of competitive inhibition of 18F-FDG uptake by d-glucose. After sporadic reports of patients with glucose levels higher than 2 g/L (10 mmol/L) who were studied successfully, it has recently been demonstrated (in a series including 123 patients with suspected infection) that neither diabetes nor hyperglycemia at the time of the study had any significant impact on the false-negative rate in this clinical scenario (123). This is different from tumor imaging, especially of pancreatic and lung cancers, for which reduced 18F-FDG uptake has been observed at 1.4 g/L (8 mmol/L) (124). Although efforts should be made to decrease blood glucose to the lowest possible level, if the study is normally indicated in those with unstable (“brittle”) or poorly controlled diabetes (often associated with infection), hyperglycemia should not represent an absolute contraindication for performing the study. Therefore we recommend the same advice and suggest registering blood glucose level and any other information that could be relevant for scan interpretation.
Kidney failure
18F-FDG imaging can be performed in patients with kidney failure, although the image quality may be suboptimal and prone to interpretation pitfalls (125).
Instructions to patients
The technologist, nurse, or physician should give the patient a thorough explanation of the test. Patients must fast (although intake of noncaloric beverages, such as water or coffee, is allowed) for at least 4 h before 18F-FDG imaging, during which time they should be encouraged to drink sufficient water to ensure hydration and promote diuresis (7). In specific situations (e.g., endocarditis), a longer fast is recommended to optimize the reduction of myocardial uptake.
Necessary medications are allowed and must be recorded. Ideally, the scan may be scheduled 3–4 h after breakfast in diabetic patients who have received their insulin early in the morning (e.g., 7:00 am). Diabetic patients should take their medications early in the morning, and the 18F-FDG imaging should be scheduled for late morning. Detailed instructions can be found in the EANM guidelines for tumor imaging. It is strongly advised that commencement of steroid treatment be avoided between the request date for the study and the appointment. The use of steroid treatment could result in a false-negative result, especially in giant cell arteritis and other systemic vasculitides (126). Because the effect of antibiotics on 18F-FDG uptake is unknown, it is important to be aware of ongoing antibiotic treatment, but no general recommendation on withdrawal can be stated.
The patient should be advised to avoid strenuous physical exercise within 24 h before injection. Patients should void before being positioned on the PET/CT table.
Preinjection clinical evaluation by the nuclear medicine physician
18F-FDG imaging recently showed high performance in critically ill patients with suspected infection (41). The management of such patients is, however, time consuming and technically challenging, requiring high-level multidisciplinary skills. If 18F-FDG imaging is scheduled in such a patient, issues concerning logistics, nursing care, and medical care should be anticipated and reviewed carefully.
The nuclear medicine physician should have available and take into account all information that could facilitate the interpretation of 18F-FDG imaging (CT, MRI, and other previously performed diagnostic imaging, including any previous PET study). In particular, the following parameters should be checked:
Fasting state (except in some diabetics who received insulin, see “Instructions to Patients: Medications”).
History of diabetes.
Patient weight and height (weight should be measured in very ill patients if feasible and if standardized uptake values [SUVs], are needed).
Fever or elevation of acute inflammatory markers such as erythrocyte sedimentation rate or C-reactive protein.
Trauma, recent surgery, or recent invasive diagnostic procedures (at least within the last 4 wk).
History of a neoplastic disorder, recent chemotherapy (many patients with previously known cancer or under treatment for cancer may be candidates for 18F-FDG imaging for nonmalignant indications), or radiation therapy (at least within the last 3 mo); bone marrow, spleen, and gastrointestinal biodistribution of 18F-FDG may vary.
Presence of a known infectious or inflammatory condition or immunosuppressive status.
Pathophysiologic disturbances and symptoms, such as diarrhea and localized pain, especially in the extremities (e.g., knee, for appropriate choice of field of view).
Presence of benign disease with high tissue proliferation.
Pregnancy or suspected pregnancy, breastfeeding, and date of the last menses.
Blood glucose level.
Patient relaxation.
Before 18F-FDG administration, the patient should relax in a waiting room to minimize muscular activity and thereby physiologic uptake of 18F-FDG in muscles. The waiting room should be at an adequate temperature (20°C–22°C), and drafts should be prevented in order to reduce uptake in brown fat. In selected cases, prevention of brown fat uptake may be enhanced by the use of β-blocking agents. Hyperventilation may cause uptake in the diaphragm, and stress-induced tension may result in increased 18F-FDG uptake in the trapezius and paraspinal muscles. Some authors have proposed administration of benzodiazepines to obtain muscle relaxation: this should be restricted to very active patients and those in whom evaluation of the neck is essential. If benzodiazepines are given, it is wise to ensure first that the patient will not drive or undertake activity that requires the patient to be alert after the procedure. Patients should avoid talking or chewing immediately before and after 18F-FDG administration to minimize 18F-FDG uptake in laryngeal and masticatory muscles.
Some of the measures mentioned above may be superfluous for small-field-of-view acquisitions, such as a limited acquisition for the evaluation of a localized infection.
C. Radiopharmaceutical
18F-FDG administered activity in Europe
The injected activity of 18F-FDG to obtain good imaging with a PET scanner operated in 3-dimensional mode is in the range of 2.5–5.0 MBq/kg, that is, 175–350 MBq or 4.7–9.5 mCi in a 70-kg standard adult, although the required dose may depend on the imaging device and the acquisition time used (6). Activities should be reduced for infants and children according to the EANM pediatric dosage card issued in 2008 (127,128) (www.eanm.org/docs/dosagecard.pdf). Higher injected activities may be required in overweight and obese patients. National limits may be less than these figures, in which case the relevant national limit should be applied. 18F-FDG should be administered intravenously, using a minimum 21-gauge indwelling catheter (or Abbott butterfly) to ensure good venous access.
18F-FDG administered activity in the United States
The 18F-FDG administered activity should be 370–740 MBq (10–20 mCi) for adults and 3.7–5.2 MBq/kg (0.10–0.14 mCi/kg) for children. Administered activity for children should be based on body weight and should be as low as reasonably achievable for diagnostic imaging. For more specific guidance on pediatric dosing, please refer to “Pediatric Radiopharmaceutical Administered Doses: 2010 North American Consensus Guidelines” (129).
When feasible, the radiopharmaceutical should be injected intravenously at a site contralateral to sites of known or suspected disease. With PET/CT, the radiation dose to the patient is the combination of the dose from the PET radiopharmaceutical and the dose from the CT portion of the study. Lower administered activities, however, may be appropriate with advancements in PET/CT technology.
Uptake period after injection
After administration of 18F-FDG, the patient should remain quiet until the start of image acquisition and void the urinary bladder as often as possible to limit radiation to the urinary tract. A minimum 60-min interval between 18F-FDG injection and acquisition is recommended to obtain adequate 18F-FDG biodistribution. During this time, the patient should drink at least 1 L of water or receive this amount intravenously to promote diuresis, if there are no contraindications. Patients should void immediately before image acquisition begins.
Postprocedure recommendations
No other recommendations (other than normal radiation protection advice) are to be made after the imaging is finished and the technical quality of the study has been checked. The patient is free to resume normal activities without further precautions, except when benzodiazepines or other depressant medications were administered or if the patient is actively breastfeeding (see “Patient Preparation and Precautions”). Patients who ask about the report should be informed that a detailed report will be produced after thorough evaluation of the 18F-FDG study and all available information.
Radiation dosimetry
The organ that receives the highest radiation dose is the urinary bladder. High absorbed doses are expected in the lactating breast, but figures are not available from the literature. The effective dose is 1.9 10−2 mSv/MBq for the PET examination (ICRP 106 (121)) in addition to CT dose, which may vary according to the type of study performed.
D. Image acquisition
It is not the aim of this guideline to discuss the performance of current PET/CT scanners. Reference is made to the 2009 EANM guideline for FDG PET and PET/CT for tumor imaging (7) and the SNMMI Guideline for Tumor Imaging with 18F-FDG PET/CT (8).
With current PET/CT scanners, the acquisition is performed in whole-body mode, using steps of 1.5–3 min per bed position. Whole-body acquisition is usually defined as a field of view covering the head to mid thigh, starting in the pelvic area, when the bladder is empty. This field of view may not be sufficient in patients with FUO, in whom continuation of the scan down to the feet may be useful, depending on the clinical suspicion.
Conversely, a limited field of view may be used, with imaging confined only to the region of the clinical problem (e.g., a hip prosthesis, an infected vascular graft, or a diabetic foot).
Although dynamic scanning has been described in orthopedic indications, it has not proven widely useful and hence is not advised at present in clinical practice. This applies also to dual-time-point early and late imaging protocols. From the available literature, dual-time-point imaging does not reliably help in differentiating infection from cancer.
CT acquisition parameters are detailed in the EANM and SNMMI tumor imaging guidelines. For PET/CT, low-dose CT should be performed for attenuation correction and anatomic localization.
For diagnostic CT, acquisition parameters should be determined according to specific radiologic society guidelines. Injection of iodinated contrast may be indicated to obtain a full PET/CT scan with a diagnostic CT sequence. However, there are not enough data to support the use of intravenous contrast in the clinical setting of infection/inflammation imaging. The use of contrast is probably indicated in FUO, postoperative fever, and vascular prostheses but not in vasculitis and orthopedic infection. In cases of contrast-enhanced CT, a low-dose CT scan before contrast injection should be obtained for attenuation correction. An alternative to acquiring 2 CT scans could be to apply contrast compensation when considering Hounsfield units.
E. Image analysis and interpretation
Physiologic 18F-FDG distribution
Accumulation of 18F-FDG can normally be seen in the brain, heart, kidneys, and urinary tract at 60 min after injection. The brain has a high uptake of 18F-FDG (7% of injected activity). The myocardium in a typical fasting state primarily uses free fatty acids but after a glucose load uses glucose. In the fasting state, 18F-FDG uptake in the myocardium should be low, but this is variable. Unlike glucose, 18F-FDG is excreted by the kidneys into the urine and accumulates in the urinary tract. 18F-FDG may also be seen in muscles, depending on recent motor activity and insulin. Uptake in the gastrointestinal tract varies from patient to patient and may be increased in patients taking metformin (130). Uptake is common in the lymphoid tissue of the Waldeyer ring and in the lymphoid tissue of the terminal ileum and cecum (131,132). Physiologic thymic uptake may be present, especially in children and young adults (133). Uptake in brown fat may be observed mainly in young patients and when the ambient temperature is low. No physiologic uptake is noted in the bone itself (unless free 18F-fluoride is present as a contaminant), but especially in infected or inflamed patients, bone marrow uptake can be noted to a variable level. This is also true in patients with hematopoietic regeneration, such as after chemotherapy, either spontaneously or after administration of hematopoietic growth factors (e.g., granulocyte–macrophage colony-stimulating factor) (134).
Qualitative analysis
PET images are visually analyzed by looking for increased 18F-FDG uptake, taking into consideration the pattern (focal, linear, diffuse), intensity, and relationship to areas of physiologic distribution. PET information is compared with morphologic information obtained by CT. It must be kept in mind that the sensitivity of 18F-FDG for infection is not absolute and that even in the case of negative PET results, a thorough interpretation of the CT scan is essential.
Quantitative analysis (SUV)
In contrast to its use in oncology, SUV has not been validated in inflammation and infection. Therefore, SUV in this field should be used with caution in clinical practice. In a single study, though, in spondylodiskitis, an SUV cutoff greater than 3 has been suggested to avoid false-positive findings (26). This criterion, however, cannot be applied for other diseases. Maximum SUV data were also analyzed for sarcoidosis (27). Although correlations were found with other parameters of disease activity, no real cutoff was derived for interpretation.
General interpretation criteria
To evaluate 18F-FDG imaging, the following should be taken into consideration:
Clinical question raised in the request for 18F-FDG imaging.
Clinical history.
Scanning protocol (with or without attenuation correction).
Physiologic distribution of 18F-FDG, and its individual variations in the specific patient evaluated.
Localization of the abnormal uptake according to anatomic imaging data.
Intensity of 18F-FDG uptake (e.g., maximum SUV and/or peak SUV).
Correlation with data from previous clinical, biochemical, and morphologic examinations.
Presence of potential causes of false-negative results (lesion size, low metabolic rate, hyperglycemia, lesions masked by adjacent high physiologic uptake, concomitant drug use interfering with uptake, such as ongoing steroid therapy in systemic disorders).
Presence of potential causes of false-positive results (injection artifacts and external contamination, reconstruction artifacts from attenuation correction, normal physiologic uptake, pathologic uptake not related to infection or inflammation).
Care should be taken in the interpretation of PET data corrected for attenuation using a low-dose CT scan (particularly when metallic material or implants are present). Assessment of both attenuation-corrected and non–attenuation-corrected images is recommended.
Interpretation criteria for specific disorders
There are no general criteria published for all inflammatory and infectious disorders. Most research articles on the subject have defined interpretation criteria for the purposes of the study. Some authors have reported specific interpretation criteria that can be used, although no definitive consensus has been agreed on.
Joint prostheses: some interpreting criteria have been proposed by Reinhartz et al. (106) for painful hip arthroplasties. The use of their criteria results in overall accuracy of 95% but has not been confirmed by others. Visual interpretation using these criteria may be more reliable than quantitative (SUV) analysis, which is not recommended.
Sarcoidosis: sarcoidosis can mimic malignancies and especially lymphoma. Keijsers et al., however, reported that a high parenchymal lung uptake (with elevated SUV) was predictive of severe disease activity, especially if the mediastinum and hilum maximum SUV was low (135). Conversely, the same authors reported that the absence of metabolic activity in the lung parenchyma was related to low-activity disease and justifies a wait-and-see policy (136).
Vascular prostheses: because physiologic uptake is often visible in vascular prostheses, patterns of interpretation have been discussed. It is now felt that linear, diffuse, and homogeneous uptake is not likely to represent infection whereas focal or heterogeneous uptake with projection over the vessel on CT is highly suggestive of infection (111).
Vasculitis: Hautzel et al. (137) and Meller et al. (138) both proposed criteria for the diagnosis of active giant cell arteritis. The criteria of Meller et al. are based on visual comparison of uptake in the aorta with that in the liver or brain but have not been used or reproduced by others. Using receiver-operating-characteristic curve analysis, Hautzel et al. defined an optimal cutoff of 1.0 for aorta-to-liver ratio to differentiate patients with giant cell arteritis from healthy patients. Although this cutoff resulted in good diagnostic performance, this parameter has also not been further evaluated by other authors.
VIII. DOCUMENTATION/REPORTING
A. Direct communication
Significant abnormalities should be verbally communicated to the appropriate health care provider if a delay in treatment might result in significant morbidity. An example of such an abnormality would be a lesion with a high risk of pathologic fracture. Other clinically significant unexpected findings should also be communicated verbally.
Reporting of abnormalities requiring urgent attention should be consistent with the policy of the interpreting physician’s local organization. Written documentation of verbal reporting should be made in the medical record, usually as part of the PET/CT report.
B. Contents of the written report
Study identification
The report should include the full name of the patient, medical record number, and date of birth. The name of the examination should also be included, with the date and time it is performed. The electronic medical record should provide these data, as well as a unique study number.
Clinical information
At a minimum, the clinical history should include the reason for referral and the specific question to be answered. If known, the diagnosis and a brief treatment history should be provided. The results of relevant diagnostic tests and prior imaging findings should be summarized.
The type and date of comparison studies should be stated. If no comparison studies are available, a statement should be made to that effect.
Procedure description
Study-specific information should include the name of the radiopharmaceutical, the dose in megabecquerels or millicuries, the route of administration (intravenous), and the date and time of administration. The site of administration is optional. The name, dose, and route of administration of regulated nonradioactive drugs and agents should also be stated. The type of camera should be specified, but specific equipment information is optional.
A description of the procedure should include the time the patient was scanned or the time interval between administration of 18F and the start time of the scan. The part of the body that is scanned should be described from the starting to the ending point. The position of the patient (supine or prone), and the position of the arms (elevated or by the sides) should be stated if nonstandard.
Description of the CT part of the examination may be limited to a statement that a low-mAs CT was performed for attenuation correction and anatomic registration of the emission images. However, findings should be reported. If CT was optimized for diagnosis, then a more complete description of the CT protocol and anatomic findings should be provided.
Routine processing parameters are usually not stated in the report, but any special circumstances requiring additional processing, such as motion correction, should be described.
Description of the findings
Significant findings should be described in a logical manner. Findings may be grouped by significance or described by body region. An integrated PET/CT report is preferred, although CT optimized for diagnosis may be reported separately. For important 18F-FDG findings, the location, extent, and intensity of abnormal uptake should be described, as well as the relevant morphologic CT findings at the site of 18F-FDG abnormalities. SUV may be used as a purely descriptive means of reporting, but the measurement should not be used to render a specific diagnosis. The integrated PET/CT report should include any detected incidental findings on the CT scan that are relevant to patient care.
Limitations should be addressed. Where appropriate, factors that can limit the sensitivity and specificity of the examination should be identified. In patients with known cancer evaluated for an episode of pyrexia, the interpretation should try to separate uptake within a site of cancer from uptake in a site of inflammation or infection. Possible sources of error include a small lesion, a low-grade infection, physiologic uptake around or along exogenous material (i.e., a foreign body aseptic reaction, such as that associated with a vascular graft), artifacts (in particular, those related to overcorrection of attenuation after contrast injection or due to metallic implants, devices, and prosthesis), physiologic uptake of 18F-FDG (in brain; myocardium and other muscles; brown fat; urinary, gastrointestinal, and oropharyngeal tracts; thymus), uptake in known or unknown malignant disease, treatment-related uptake (after chemotherapy and radiation therapy and in healing surgical wounds up to 8 wk, scars, stoma, and tube placements), and aseptic inflammatory reactive 18F-FDG uptake (lymph node uptake in sterile arthritis such as rheumatoid arthritis, reactive lymph nodes in HIV-positive patients, and following immunization; atherosclerotic plaques, bone fractures, granulation tissue).
Impression
The most probable diagnosis should be given whenever possible. A differential diagnosis should be given when appropriate. When appropriate, follow-up and additional diagnostic studies should be recommended to clarify or confirm the impression.
C. Issues requiring further clarification
Controversy still remains on the role of 18F-FDG in infection and inflammation in the presence of artifacts caused by metallic implants and prostheses and the added value of SUV in improving the diagnostic accuracy of reporting. Strategies for differentiating infection from sterile inflammation need to be developed. The utility of 18F-FDG in monitoring response to antibacterial or antiinflammatory therapy is not known.
IX. EQUIPMENT SPECIFICATION
See SNMMI Guideline for Tumor Imaging with 18F-FDG PET/CT.
X. QUALITY CONTROL AND IMPROVEMENT; SAFETY, INFECTION CONTROL, AND PATIENT EDUCATION CONCERNS
Policies and procedures related to quality, patient education, infection control, and safety should be developed and implemented in accordance with national rules in Europe and with the SNMMI policies on quality control, and patient education in the United States, where appropriate.
In all patients, the lowest exposure factors should be chosen that will produce images of diagnostic quality.
Equipment performance monitoring should be in accordance with “ACR Technical Standard for Medical Nuclear Physics Performance Monitoring of PET/CT Imaging Equipment” in the United States and in accordance with national rules in Europe.
See also “FDG PET and PET/CT: EANM Procedure Guidelines for Tumour PET Imaging: version 1.0,” the SNMMI Guideline for General Imaging, the SNMMI Guideline for Use of Radiopharmaceuticals, and the SNMMI Guideline for Tumor Imaging with 18F-FDG PET/CT for equipment performance guidelines and quality control.
XI. RADIATION SAFETY IN IMAGING
See the SNMMI Guideline for General Imaging, “FDG PET and PET/CT: EANM Procedure Guidelines for Tumour PET Imaging: version 1.0,” and Tables 2 and 3.
Radiation Dosimetry for Adults (121)
Radiation Dosimetry for Children (5 Years Old) (121)
A. The pregnant or potentially pregnant patient (Table 4)
The ICRP reports that the administration of 259 MBq (7 mCi) of 18F-FDG results in an absorbed radiation dose of 4.7 mGy to the nongravid uterus (i.e., 1.8 × 10−2 mGy/MBq) (121). Direct measurements of 18F-FDG uptake in 1 case study suggested somewhat higher doses than currently provided in standard models (120). More detailed information, including information on changes with the stage of gestation, has been previously reported (130,131).
B. The breastfeeding patient
The ICRP does not recommend interruption of breastfeeding after 18F-FDG administration since little 18F-FDG is excreted in the milk (121). However, the suggestion may be made that contact between mother and child be limited for 12 h after injection of 18F-FDG to reduce the radiation dose the infant receives from external exposure to breast uptake in the mother. It is recommended that the infant be breastfed just before injection, to maximize the time between the injection and the next feeding. Milk pumped from the breast may also be fed to the infant via a bottle to avoid close contact with 18F decay in breast tissue.
C. Issues related to the CT radiation dose from PET/CT
With PET/CT, the radiation dose to the patient is the combination of the radiation dose from the PET radiopharmaceutical and the radiation dose from the CT portion of the study. Radiation dose in diagnostic CT has attracted considerable attention in recent years, in particular for pediatric examinations. It can be misleading to quote a “representative” dose for a CT scan because of the wide diversity of applications, protocols, and CT systems. This also applies to the CT component of a PET/CT study. For example, a body scan may include protocols to reduce the radiation dose to the patient or to optimize the CT for diagnostic purposes. The effective dose could range from approximately 5 to 80 mSv (0.5–8.0 rem) for these options. It is therefore advisable to estimate the CT dose specific to the CT system and protocol.
Pediatric and adolescent patients should have their CT examinations adjusted for patient size, since radiation dose to the patient increases significantly as the diameter of the patient decreases.
The effective dose for whole-body CT performed for attenuation correction and registration of emission images is in the range of 3.2 mSv (0.32 rem), using the following parameters: voltage of 120 kV, current of 30 mAs, rotation of 0.5 s, and pitch of 1. In all cases, adaptive CT dose tools (as now proposed by most manufacturers) are recommended to reduce the radiation exposure, especially in young patients.
Acknowledgments
The Committee on SNMMI Guidelines consists of the following individuals: Kevin J. Donohoe, MD (Beth Israel Deaconess Medical Center, Boston, MA); Sue Abreu, MD (Sue Abreu Consulting, Nichols Hills, OK); Helena Balon, MD (Beaumont Health System, Royal Oak, MI); Twyla Bartel, DO (UAMS, Little Rock, AR); David Brandon, MD (Emory University/Atlanta VA, Atlanta, GA); Paul E. Christian, CNMT, BS, PET (Huntsman Cancer Institute, University of Utah, Salt Lake City, UT); Dominique Delbeke, MD (Vanderbilt University Medical Center, Nashville, TN); Vasken Dilsizian, MD (University of Maryland Medical Center, Baltimore, MD); James R. Galt, PhD (Emory University Hospital, Atlanta, GA); Jay A. Harolds, MD (OUHSC-Department of Radiological Science, Edmond, OK); Aaron Jessop, MD (UT MD Anderson Cancer Center, Houston, TX); David H. Lewis, MD (Harborview Medical Center, Seattle, WA); J. Anthony Parker, MD, PhD (Beth Israel Deaconess Medical Center, Boston, MA); James A. Ponto, RPh, BCNP (University of Iowa, Iowa City, IA); Lynne T. Roy, CNMT (Cedars/Sinai Medical Center, Los Angeles, CA); Heiko Schoder, MD (Memorial Sloan-Kettering Cancer Center, New York, NY); Barry L. Shulkin, MD, MBA (St. Jude Children’s Research Hospital, Memphis, TN); Michael G. Stabin, PhD (Vanderbilt University, Nashville, TN); and Mark Tulchinsky, MD (Milton S. Hershey Medical Center, Hershey, PA).
The EANM Executive Committee consists of the following individuals: Emilio Bombardieri, MD (Foundation IRCCS “Istituto Nazionale Tumori,” Milano, Italy); Patrick Bourguet, MD (CRLCC Centre Eugene Marquis, Rennes, France); Arturo Chiti, MD (Istituto Clinico Humanitas, Milan, Italy); Jure Fettich, MD (University Medical Center Ljubjana, Ljubjana, Slovenia); Savvas Frangos, MD (Bank of Cyprus Medical Center, Nicosia, Cyprus); Dominique Le Guludec, MD (Hopital Bichat, Paris, France); and Johan F. Verzijbergen, MD (Erasmus MC, Rotterdam, The Netherlands).
XIV. APPROVAL
This practice guideline was approved by the Board of Directors of the SNMMI on November 15, 2012.
Footnotes
Published online Jan. 28, 2013.
↵* NOTE: FOR CE CREDIT, YOU CAN ACCESS THIS ACTIVITY THROUGH THE SNMMI WEB SITE (http://www.snmmi.org/ce_online) THROUGH APRIL 2016.
- © 2013 by the Society of Nuclear Medicine and Molecular Imaging, Inc.
XIII. REFERENCES
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- Received for publication August 8, 2012.
- Accepted for publication August 8, 2012.
Jump to section
- Article
- PREAMBLE
- I. INTRODUCTION
- II. GOALS
- III. DEFINITIONS
- IV. COMMON CLINICAL INDICATIONS
- V. REGULATORY ISSUES
- VI. QUALIFICATIONS AND RESPONSIBILITIES OF PERSONNEL
- VII. PROCEDURE/SPECIFICATIONS OF THE EXAMINATION
- VIII. DOCUMENTATION/REPORTING
- IX. EQUIPMENT SPECIFICATION
- X. QUALITY CONTROL AND IMPROVEMENT; SAFETY, INFECTION CONTROL, AND PATIENT EDUCATION CONCERNS
- XI. RADIATION SAFETY IN IMAGING
- Acknowledgments
- XIV. APPROVAL
- Footnotes
- XIII. REFERENCES
- Figures & Data
- Info & Metrics
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